Control device for a pneumatically operated fastener machine

ABSTRACT

In a pneumatically operated fastener machine of the type having a working cylinder and a piston reciprocable therein, the upper end of the cylinder permanently communicates with a source of compressed air and the lower end of the cylinder via a manually operated control valve alternately communicates with said source of compressed air or with the atmosphere. In the bottom of the cylinder vent passages communicating with the atmosphere are provided. During the working stroke of the piston the vent passages are open, and during the return motion of the piston the vent passages are closed by an annular valve.

United States Patent [72] Inventors Dieter Volkmann Leinstrasse 49, Neustadt/Rbge; Jurgen Korth, Birkemv '7, Berenbostel, both of, Germany [21] Appl. No. 837,135

[22] Filed June 27, 1969 [45] Patented June 15, 1971 [32] Priority June 29, 1968 [33] Germany 54] CONTROL DEVICE FOR A PNEUMATICALLY OPERATED F ASTENER MAHINE Primary Examiner-Granville Y. Custer, Jr. Attorney-Hibben, Noyes and Bicknell ABSTRACT: In a pneumatically operated fastener machine of the type having a working cylinder and'a piston reciprocable therein, the upper end of the cylinder permanently communicates with a source of compressed air and the lower end of the cylinder via a manually operated control valve alternately communicates with said source of compressed air or with the atmosphere. In the bottom of the cylinder vent passages communicating with the atmosphere are provided. During the working stroke of the piston the vent passages are open, and during the return motion of the piston the vent passages are closed by an annular valve.

PATENTED JUN 1 5 i971 SHEET 2 BF 2 CONTROL DEVICE FOR A PNEUMATICALLY OPERATED FASTENER MACHINE BACKGROUND OF THE INVENTION The invention relates to a control device for a pneumatically operated fastener machine and, more particularly, for a portable tool for driving fastener means into a workpiece.

The prior art pneumatically operated machines of this type comprise a permanently open duct for admission of compressed air to the upper end of a working cylinder, in which a piston performs a reciprocating motion. The lower end of the working cylinder is filled with compressed air via a second duct and a manually operated valve to return the piston to and maintain it in its initial position The effective lower face of the piston is larger than its upper face, and therefore the air under pressure acting on the lower piston face moves the piston to its retracted initial position. During the working stroke the lower face of the piston communicates with the atmosphere and the compressed air solely acts upon the upper face of the piston and thereby brings about a movement of the piston in its staple driving direction. During the working stroke the air contained in the lowerpart of the cylinder beneath the piston is displaced by the piston and can only be vented by said second duct. This duct however provides a high resistance of flow for the air streaming out. Therefore, during the driving stroke a counterpressure of air is developed in the cylinder whereby the striking power and efficiency of the fastener machine are reduced.

It is an important object of the present invention to provide a pneumatically operated fastener machine, the piston of which during its working stroke is not exposed to any counterpressure, resulting from the air which is displaced by said piston.

Still another object of the invention is the provision of a fastener device with a high efficiency and high striking power.

It is a further object of the present invention to provide a portable pneumatic stapler of simple construction, which is easy to operate and comfortable to handle.

These and other objects and features of the invention will become apparent from the following detailed description in conjunction with the drawings in which one embodiment of the invention is shown, it being understood that the present description is merely chosen by way of an example.

In the accompanying drawings:

FIG. 1 is a partial longitudinal sectional view of a pneumatically operated fastener machine, embodying the present invention, with its parts in the position during the return motion of the piston;

FIG. la is a partial sectional view of a modification of the invention in the position of parts according to FIG. 1; FIG. 2 is the sectional view of FIG. 1 with the parts represented in the position of the piston after having finished its working stroke;

FIG. 2a is the sectional view of the modification shown in FIG. la in the position of the parts according to FIG. 2.

An essential feature of the present invention is the provision of orifices forming part of the vent passage in the housing directly below the bottom wall of the cylinder of the pneumatically operated fastener machine. The orifices during the working stroke of the piston are in open communication with the atmosphere and during the return motion of the piston as well as when the piston is in its retracted initial position the orifices are closed by an annular outlet valve.

It is advantageous to provide the annular valve with a flat pistonlike shape. This annular valve-piston is movable in the direction of the cylinder axis. On both sides of said valvepiston compressed air is admitted. The effective lower surface of said annular valve-piston is larger than the upper surface which is adjacent to the piston so that when exposed to equal air pressure on both surfaces the valve-piston is raised and closes the orifices.

According to another feature of the invention and in order that the working cylinder can be supplied with the air which is necessary for the return motion of the piston, the annular valve is provided with ports for the flow of air under pressure. The channel for the supply of this compressed air may be arranged at the lower surface of the annular valve which is adjacent to the bottom wall of the housing enclosing the working cylinder.

In a fastener machine according to the present invention, the orifices provided adjacent the bottom wall of the cylinder for its ventilation are of such size that the air displaced by the piston during its working stroke may escape nearly without any resistance to flow. Thereby the compressed air permanently acting upon the upper face of the piston is fully effective in that the piston is immediately accelerated. Consequently a high velocity and a high kinetic energy are imparted to the piston, thereby providing for a high striking power of the piston the mass of which may be kept small. Thus, a light weight and handy machine is obtained.

Referring now to FIG. 1 of the drawings, the operated portable pneumatic device or machine according to the invention consists of a housing body 1, shaped as a handle. The housing body encloses an air chamber 2 which is connected to a supply of compressed air (not shown in the drawing). A working cylinder 3 forms a part of the housing body 1 and contains a piston 4 reciprocable therein.

In the lower portion of the working cylinder 3 is arranged an elastic bumper 5 which is secured to the bottom wall 6 of cylinder 3. At its lower face bottom wall 6 is shaped as a seat for an annular pistonlike valve 7 which has a central opening and is slidably guided on a drive track 8 in which a driver 9 is reciprocably guided. The valve-piston 7 is provided with passages 10 for compressed air to be admitted to the working cylinder 3 beneath piston 4. An annular shoulder 11 on the lower face of valve-piston 7 engages an annular groove 14 in the foot piece or bottom portion 13 of the housing for the working cylinder 3 during the working stroke of piston 4 and thereby closes a duct 12 which duct connects the space underneath the valve-piston 7 with a control valve 15. Said control valve is provided witha ball valve for blocking the compressed air supply from air chamber 2 and is manually actuated by a trigger lever 16.

The effective upper face of piston 4 upon which compressed air from air chamber 2 is acting, is made smaller than the lower piston face by a hollow cylindrical extension 17 which is secured to the upper face of piston 4 and which is guided in a housing projection 18. In a cover 19 of the housing projection 18 a vent hole 20 is provided. The hollow cylindrical extension 17, by an elastic sealing ring is sealed against the housing projection 18 which by the vent hole 20 communicates with the open atmosphere. The housing below the bottom portion of working cylinder 3 is provided with radial orifices 21 which communicate with the atmosphere.

If the trigger lever 16 is moved upwards to actuate a working stroke of the machine as is illustrated in FIG. 2, control valve 15 closes the compressed air supply from air chamber 2 to duct 12 and at the same time connects duct 12 to the atmosphere via the clearance between the rod and the body of control valve 15. Thereby the space beneath valve-piston 7 also communicates with the atmosphere and valve-piston 7 is moved downwards by the compressed air contained in the working cylinder 3 underneath piston 4 and acting upon the upper face of valve-piston 7. In the position of valve-piston 7, represented in FIG. 2, the orifices 21 are opened and the air which is displaced by piston 4 during its working stroke is vented to the atmosphere through an opening in the bottom wall 6 and thence through the orifices 21. The orifices 21 have a relatively large cross section and therefore the air pressure underneath piston 4 reduces so quickly that driver 9 is instantaneously moved by piston 4 with a high velocity in the direction of the driving stroke. Also, as shown in FIGS. 1 and 2, the orifices 21 are preferably shaped as diffusers with tapered wall portions providing an outwardly divergent or enlarging cross section in the direction of flow of the air being vented.

As is shown in FIGS. la and 2a the annular shoulder ll on the lower face of valve-piston 7 may be omitted and the annular valve-piston 7 may be shaped with a flat lower surface. In this structure the compressed air is prevented from flowing back by a flat elastic annular disc 22, which by a safety ring 23 is secured to the hub of annular valve-piston 7. This elastic annular disc 22 operates as a check valve for the passages 10 and prevents an undesired retum flow of air from the space beneath valve-piston 7 to the lower portion of working cylinder 3.

It is apparent that the examples shown above have been given solely by way of illustration and not by way of limitation and that they are subject to many variations and modifications within the scope of the present invention. All such variations and modifications are to be included within the scope of the present invention.

We claim:

1. In a pneumatic fastener driving device comprising a housing body, a cylinder in'said housing body having an upper end and a lower end, a piston reciprocable in said cylinder, said piston having an upper surface and a lower surface, said lower surface being larger than said upper surface, a driver fixed to said piston for driving a fastener, a drive track in said cylinder guiding said driver, said housing body having an air chamber communicating with a source of compressed air, a permanently open duct betweensaid air chamber and said upper end of said cylinder, a second duct communicating at one end with said lower end of the cylinder, and a manually operated control valve for connecting the opposite end of said second duct selectively either with said air chamber or with the atmosphere, said control valve when in its unactuated position connecting said opposite end of said second duct with said air chamber whereby compressed air acts upon the lower surface of said piston for causing a return stroke and maintaining said piston in a retracted initial position, and said control valve, when in its actuated position connecting said opposite end of said second duct with the atmosphere whereby compressed air acts solely upon the upper surface of said piston causing an immediate movement of said piston in a working stroke; the improvement comprising vent passage means connecting said lower end of said cylinder with the atmosphere, and an outlet valve movable along the axis of said cylinder adjacent said lower end thereof and cooperable with said vent passage means for opening and closing the same, said outlet valve.

comprising an annular member having two piston faces, one of said faces beingsmaller than the other of said faces, said smaller face being acted upon by compressed air in said cylinder to open said vent passage means when said control valve is in its actuated position, and said other or larger face being acted upon by compressed air supplied to said lower end of said cylinder to close said vent passage means when said control valve is in its unactuated position.

2. The device of claim 1, wherein said cylinder has a bottom wall at said lower end thereof, said vent passage means including an opening in said bottom wall, said opening being closed by said smaller face of said outlet valve when compressed air supplied through said second duct acts upon said larger face of said outlet valve, and said outlet valve being movable away from said opening when compressed air in said cylinder acts upon said smaller face and the space below said larger face communicates with the atmosphere through said second duct.

3. The device of claim 2, wherein said housing body has a bottom portion spaced from said bottom wall of said cylinder, said outlet valve is movably disposed in said housing body between said bottom wall and said bottom portion, and said one end of said second duct communicates with said housing body between said bottom portion and said larger face of said outlet valve.

4. The device of claim 2, wherein said vent passage means also includes radial orifices in said housing body below said bottom wall of said cylinder.

5. The device of claim 4, wherein said radial orifices are shaped as diffusers having an outwardly divergent cross section.

6. The device of claim 1, wherein said outlet valve has a valve passage therethrough between said faces for supplying compressed air from said second duct to said lower end of said cylinder.

7. The device of claim 6, wherein an annular groove is provided in said housing body below said lower end of said cylinder, and said outlet valve has an annular shoulder on said larger face for engaging said groove and sealing off said second duct from said valve passage during a working stroke.

8. The device of claim 6, wherein said outlet valve is provided with a check valve for closing said valve passage during a working stroke.

9. The device of claim 8, wherein said check valve comprises an elastic annular disc secured to said outlet valve and overlying said valve passage.

10. The device of claim 1, wherein said drive track is disposed coaxially in said cylinder and said annular member comprising said outlet valve has a central opening and is slidably guided on said drive track. 

1. In a pneumatic fastener driving device comprising a housing body, a cylinder in said housing body having an upper end and a lower end, a piston reciprocable in said cylinder, said piston having an upper surface and a lower surface, said lower surface being larger than said upper surface, a driver fixed to said piston for driving a fastener, a drive track in said cylinder guiding said driver, said housing body having an air chamber communicating with a source of compressed air, a permanently open duct between said air chamber and said upper end of said cylinder, a second duct communicating at one end with said lower end of the cylinder, and a manually operated control valve for connecting the opposite end of said second duct selectively either with said air chamber or with the atmosphere, said control valve when in its unactuated position connecting said opposite end of said second duct with said air chamber whereby compressed air acts upon the lower surface of said piston for causing a return stroke and maintaining said piston in a retracted initial position, and said control valve, when in its actuated position connecting said opposite end of said second duct with the atmosphere whereby compressed air acts solely upon the upper surface of said piston causing an immediate movement of said piston in a working stroke; the improvement comprising vent passage means connecting said lower end of said cylinder with the atmosphere, and an outlet valve movable along the axis of said cylinder adjacent said lower end thereof and cooperable with said vent passage means for opening and closing the same, said outlet valve comprising an annular member havinG two piston faces, one of said faces being smaller than the other of said faces, said smaller face being acted upon by compressed air in said cylinder to open said vent passage means when said control valve is in its actuated position, and said other or larger face being acted upon by compressed air supplied to said lower end of said cylinder to close said vent passage means when said control valve is in its unactuated position.
 2. The device of claim 1, wherein said cylinder has a bottom wall at said lower end thereof, said vent passage means including an opening in said bottom wall, said opening being closed by said smaller face of said outlet valve when compressed air supplied through said second duct acts upon said larger face of said outlet valve, and said outlet valve being movable away from said opening when compressed air in said cylinder acts upon said smaller face and the space below said larger face communicates with the atmosphere through said second duct.
 3. The device of claim 2, wherein said housing body has a bottom portion spaced from said bottom wall of said cylinder, said outlet valve is movably disposed in said housing body between said bottom wall and said bottom portion, and said one end of said second duct communicates with said housing body between said bottom portion and said larger face of said outlet valve.
 4. The device of claim 2, wherein said vent passage means also includes radial orifices in said housing body below said bottom wall of said cylinder.
 5. The device of claim 4, wherein said radial orifices are shaped as diffusers having an outwardly divergent cross section.
 6. The device of claim 1, wherein said outlet valve has a valve passage therethrough between said faces for supplying compressed air from said second duct to said lower end of said cylinder.
 7. The device of claim 6, wherein an annular groove is provided in said housing body below said lower end of said cylinder, and said outlet valve has an annular shoulder on said larger face for engaging said groove and sealing off said second duct from said valve passage during a working stroke.
 8. The device of claim 6, wherein said outlet valve is provided with a check valve for closing said valve passage during a working stroke.
 9. The device of claim 8, wherein said check valve comprises an elastic annular disc secured to said outlet valve and overlying said valve passage.
 10. The device of claim 1, wherein said drive track is disposed coaxially in said cylinder and said annular member comprising said outlet valve has a central opening and is slidably guided on said drive track. 